The appName parameter was introduced in Revulytics Usage Integlligence SDK version 5 and is used when creating the SDK config and log files. Multiple applications or plugins which are being tracked under the same product ID and which create separate instances of the SDK should use a different appName value. This way a different set of config and log files are created for each instance, avoiding the possibility of a conflict when syncing with the server and writing to these files if multiple instances are running in parallel.
The appName is only used by the SDK and although different config files are created for each instance they will still be tracked by the server as a single installation. This means that when setting product data such as version, build and edition, all instances should set the same values. If different values are set by each instance they will overwrite each other and only the last value synced per day is saved by the server and made available in the reports. If different values for the same property need to be tracked by each instance, it is recommend to make use of custom properties where each application or plugin can have a separate custom property assigned to it.